A method for preparing a broadband electromagnetic wave absorbing metamaterial with layered metal hydroxide grown on the surface of a nickel metal mesh.

Abstract

This invention relates to a method for preparing a broadband electromagnetic wave absorbing metamaterial of layered metal hydroxide grown on the surface of a nickel metal mesh, belonging to the fields of materials science and engineering technology and electromagnetic shielding. The LDH coating prepared by this method is mainly used in research on microwave absorbing materials for military and civilian applications. The molecular formula of the LDH layer is... M 1 - x 2 + M x 3 + O H 2 x + A m - x / m ⋅ n H 2 O x M 2+ It can represent a divalent metal cation (e.g., Mg). 2+ Ca 2+ Zn 2+ (etc.), M 3+ It can represent trivalent metal cations (e.g., Al). 3+ Fe 3+ The technology used in this invention is simple to operate and requires little time. The samples obtained by this invention have strong absorption capacity, wide absorption bandwidth, thin thickness, light weight, stable structure and chemical properties, and good environmental friendliness.

Description

Technical Field

[0001] This invention relates to methods for preparing LDHs electromagnetic wave absorbing materials using bubble template method and hydrothermal synthesis method, belonging to the fields of materials science and engineering technology and electromagnetic shielding. Background Technology

[0002] Electromagnetic waves are an unavoidable new source of pollution arising from the development of information technology. The widespread use of wireless communication in daily life, such as televisions, radios, mobile phones, and other mobile electronic products, generates many unnecessary electromagnetic signals in the environment, which can adversely affect human health, the environment, and equipment. Therefore, the demand for absorbing materials has become an increasingly urgent issue. Generally, effective EMI shielding materials are governed by three main functions: reflection, absorption, and multiple reflections. Electromagnetic wave reflection typically occurs at the surface of conductive materials and is related to the relative impedance mismatch between the shielding surface and the propagating wave. When electromagnetic waves enter the interior of the material, absorption losses occur due to ohmic losses generated by the induced current and heat generation within the material. The reflection and absorption performance of EMI shielding materials both depend on high conductivity. Multiple reflections occur because electromagnetic waves are trapped between two boundaries due to repeated reflections. Recently, various high-performance EMI shielding materials, such as nanofibers, carbon-based materials, and transparent materials, have been studied.

[0003] Layered double hydroxides (LDHs) are metal hydroxides with a layered structure composed of multiple metal elements in various valence states. They mainly include two types: hydrotalcite and hydrotalcite-like compounds, whose chemical composition and microstructure are tunable. Research shows that microstructure has a significant impact on the microwave absorption properties of nanomaterials. Nickel nanopowders possess excellent magnetic properties, and their morphology and grain size greatly influence these properties. For LDHs, the lamellar structure has a positive charge, and the interlayers are composed of various anions and water molecules. The lamellar metal elements can be dispersed at the atomic level, and the types and proportions of lamellar metal elements, the types of interlayer anions, the lamellar structure, and the interlayer spacing are easily controlled, making them feasible precursors for functionalized composite materials. The products of hydrotalcite calcination are oxides, spinels, and alloys with good magnetic properties. The topological transformation processes that occur in LDHs at different temperatures can form uniformly structured ultrafine alloys and metal oxides. The heterogeneous interfacial structure between these alloys facilitates electron transfer and can be used as a component of electromagnetic wave absorbing materials. Summary of the Invention

[0004] 1. Objective of this invention

[0005] A method for preparing a broadband electromagnetic wave absorbing metamaterial by growing layered metal hydroxides on the surface of a nickel metal mesh. These layered bimetallic hydroxides (LDHs) are synthesized by hydrothermal treatment of a metal salt solution, exhibiting good crystallinity, magnetic properties, and high electromagnetic wave absorption performance, and are easy to process.

[0006] 2. Key Invention Points of this Technology

[0007] The key points of this invention are as follows:

[0008] 1. A method for preparing LDHs electromagnetic wave absorbing materials using hydrothermal synthesis, characterized in that the method includes the following steps:

[0009] (1) Select a suitable metal mesh substrate, among which nickel metal mesh and copper metal mesh have high ductility and good plasticity;

[0010] (2) Cut the 100-mesh Ni metal mesh into 4cm×2cm sizes, clean the surface with ultrapure water, and ultrasonically treat the Ni metal mesh with anhydrous ethanol and dilute hydrochloric acid.

[0011] (3) In this invention, boric acid is used as a buffer, sodium dodecyl sulfate as an additive, and NiCl2·6H2O and NH4Cl are used as raw materials. NiCl2·6H2O and NH4Cl are completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl2·6H2O and a concentration of 2 mol / L for NH4Cl. After stirring evenly, an electrodeposition electrolyte is obtained. Porous nickel (PN) is then synthesized on a nickel mesh using a bubble template method. The positive electrode is connected to a metallic nickel mesh, and the negative electrode is connected to a carbon rod. The current density is 1 A·cm⁻¹. -2 0.8A·cm -2 0.6A·cm -2 0.4A·cm -2 0.2A·cm -2 The electrodeposition times were 300s, 600s, 900s, 1200s, and 1500s;

[0012] (4) LDHs were prepared on a PN substrate by hydrothermal synthesis using trisodium citrate (C6H5Na3O7) as a complexing agent, deionized water as a solvent, and metal salts Ni(NO3)2·6H2O and Fe(NO3)3·9H2O as raw materials. Specific masses of metal salts Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were completely dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol, respectively. Then, 0.25 mmol of trisodium citrate was added, and the mixture was stirred uniformly to obtain a precursor solution. This solution was transferred to a reaction vessel, porous nickel was added, and the mixture was kept at 150°C for 48 h. After the incubation period, the product was cooled, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the NiFe LDH product. Attached Figure Description

[0013] Figure 1 Comparison of electromagnetic absorption properties between nickel mesh and porous nickel

[0014] Figure 2 SEM image of PN

[0015] Figure 3 SEM images of NiFe LDH Detailed Implementation

[0016] Based on the study of the hydrothermal synthesis method, the factors affecting the performance of products prepared by this method are as follows:

[0017] ① Metal salt ion concentration ratio

[0018] ② Hydrothermal reaction temperature

[0019] ③ Concentration of trisodium citrate (complexing agent)

[0020] ④ Hydrothermal reaction time, etc.

[0021] The following describes embodiments of the method of the present invention:

[0022] Example 1

[0023] Preparation of NiFe LDH on Ni metal mesh surface.

[0024] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Fe-LDHs product.

[0025] Example 2

[0026] Preparation of NiFe LDH on Ni metal mesh surface.

[0027] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2 Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 10 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Fe-LDHs product.

[0028] The nickel-iron ratio has a significant impact on the morphology, crystallinity, magnetic properties, and adsorption performance of the product.

[0029] Example 3

[0030] Preparation of NiCu LDH on Ni metal mesh surface.

[0031] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Cu(NO3)2·3H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Cu-LDHs product.

[0032] Example 4

[0033] Preparation of NiCo LDH on Ni metal mesh surface.

[0034] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2 Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Co(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Co-LDHs product.

[0035] Example 5

[0036] Preparation of NiMn LDH on Ni metal mesh surface.

[0037] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Mn(NO3)2·4H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Mn-LDHs product.

[0038] Example 6

[0039] Preparation of NiFe LDH on Ni metal mesh surface.

[0040] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2 Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.125 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Fe-LDHs product.

[0041] Example 7

[0042] Preparation of NiFe LDH on Ni metal mesh surface.

[0043] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 200 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Fe-LDHs product.

[0044] Example 8

[0045] Preparation of NiFe LDH on Ni metal mesh surface.

[0046] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2 Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 72 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Fe-LDHs product.

[0047] Example 9

[0048] Preparation of NiFe LDH on Ni metal mesh surface.

[0049] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble-templating method, with an electrodeposition current density of 0.8 A·cm⁻¹. -2Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Fe-LDHs product.

[0050] Example 10

[0051] Preparation of NiFe LDH on Ni metal mesh surface.

[0052] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble-templating method, with an electrodeposition current density of 0.6 A·cm⁻¹. -2 Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Fe-LDHs product.

[0053] Example 11

[0054] Preparation of NiFe LDH on Ni metal mesh surface.

[0055] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble-templating method, with an electrodeposition current density of 0.6 A·cm⁻¹. -2Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Fe-LDHs product.

[0056] Example 12

[0057] Preparation of NiFe LDH on Ni metal mesh surface.

[0058] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2 Electrodeposition time was 600 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Fe-LDHs product.

[0059] Example 13

[0060] Preparation of NiFe LDH on Ni metal mesh surface.

[0061] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2Electrodeposition time was 900 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Fe-LDHs product.

[0062] Example 14

[0063] Preparation of NiCu LDH on Ni metal mesh surface.

[0064] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2 Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Cu(NO3)3·3H2O, and urea were weighed and dissolved in deionized water to concentrations of 10 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Cu-LDHs product.

[0065] Example 15

[0066] Preparation of NiCu LDH on Ni metal mesh surface.

[0067] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Cu(NO3)3·3H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.125 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Cu-LDHs product.

[0068] Example 16

[0069] Preparation of NiCu LDH on Ni metal mesh surface.

[0070] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2 Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Cu(NO3)3·3H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 200 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Cu-LDHs product.

[0071] Example 17

[0072] Preparation of NiCu LDH on Ni metal mesh surface.

[0073] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Cu(NO3)3·3H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 72 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Cu-LDHs product.

[0074] Example 18

[0075] Preparation of NiCu LDH on Ni metal mesh surface.

[0076] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble-templating method, with an electrodeposition current density of 0.8 A·cm⁻¹. -2 Electrodeposition time was 300 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Cu(NO3)3·3H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol respectively. 0.125 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Cu-LDHs product.

[0077] Example 19

[0078] Preparation of NiCu LDH on Ni metal mesh surface.

[0079] First, NiCl₂·6H₂O and NH₄Cl were completely dissolved in ultrapure water, with a concentration of 0.1 mol / L for NiCl₂·6H₂O and 2 mol / L for NH₄Cl. Porous nickel (PN) was then synthesized on a nickel mesh using a bubble template method, with an electrodeposition current density of 1 A·cm⁻¹. -2Electrodeposition time was 600 s to obtain PN. Then, certain amounts of Ni(NO3)2·6H2O, Cu(NO3)3·3H2O, and urea were weighed and dissolved in deionized water to concentrations of 15 mmol, 5 mmol, and 35 mmol, respectively. 0.25 mmol of trisodium citrate was added, and the mixture was stirred until homogeneous to obtain a precursor solution, which was allowed to stand for 24 h. The solution was then placed in a reaction vessel, porous nickel was added, and the mixture was kept at 150 °C for 48 h. After the incubation period, the mixture was cooled, centrifuged, washed three times with water, washed once with anhydrous ethanol, and dried at room temperature to obtain the porous nickel-based Ni-Cu-LDHs product.

Claims

1. A method for preparing a broadband electromagnetic wave absorbing metamaterial with layered metal hydroxide grown on the surface of a nickel metal mesh, characterized in that... The method includes the following steps: (1) Select a suitable metal mesh substrate, among which nickel metal mesh has high ductility and good plasticity; (2) Cut the 80-mesh Ni metal mesh into 4cm×2cm sizes, clean the surface with ultrapure water, and ultrasonically treat the Ni metal mesh with anhydrous ethanol and dilute hydrochloric acid. (3) Boric acid was used as a buffer, sodium dodecyl sulfate as an additive, and NiCl2·6H2O and NH4Cl were used as raw materials, wherein the concentration of NiCl2·6H2O was 0.1 mol / L and the concentration of NH4Cl was 2 mol / L; porous nickel was formed on a nickel mesh by a bubble template method, wherein the positive electrode was connected to a metallic nickel mesh and the negative electrode was connected to a carbon rod, and the current density was 1.0 A cm⁻¹. -2 0.8 A cm -2 0.6 A cm -2 0.4 A cm -2 0.2 A cm -2 The electrodeposition times were 300s, 600s, 900s, 1200s, and 1500s; (4) Using trisodium citrate (C6H5Na3O7) as a complexing agent, deionized water as a solvent, and metal salts Ni(NO3)2·6H2O and Fe(NO3)3·9H2O as raw materials, LDHs were prepared on a porous nickel substrate by hydrothermal synthesis. A specific mass of metal salts Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and urea were completely dissolved in deionized water, and then trisodium citrate was added. After uniform stirring, a precursor solution was obtained, which was transferred to a reaction vessel, porous nickel was added, and the mixture was kept at 150℃ for 48 h. After the heat preservation was completed, the product was cooled, washed with water 3 times, washed with anhydrous ethanol once, and dried at room temperature to finally obtain the NiFe LDH product.

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